Guanidino, thioureido, isothioureido and nitrovinylamino derivatives of pyridine

ABSTRACT

The compounds are C2-C8 straight chain alkanes terminally substituted, symmetrically or unsymmetrically, by N-(N&#39;-substituted guanidino), N-(N&#39;,N&#39;&#39;-disubstituted guanidino), N-(N&#39;-substituted thioureido), N-(nitromethylene amidino) or S-(N-substituted isothioureido)groups. Two compounds of the invention are 1,3-bis-[N&#39;-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino]propane and 1,3-bis-[S-(N-2-(5-methyl-4-imidazolylmethylthio)ethyl)isothioureido]p ropane. The compounds of this invention are inhibitors of H-2 histamine receptors.

This is a division of application Ser. No. 678,564 filed Apr. 20, 1976 now U.S. Pat. No. 4,070,472, which is a division of Ser. No. 542,971 filed Jan. 22, 1975 mow U.S. Pat. No. 3,968,227.

This invention relates to new compounds having pharmacological activity. These compounds are inhibitors of H-2 histamine receptors. In addition, this invention relates to pharmaceutical compositions comprising these compounds and to methods of inhibiting H-2 histamine receptors by administering these compounds. The compounds of this invention can exist as the addition salts but, for convenience, reference will be made throughout this specification to the parent compounds.

Many of the physiologicaly active substances within the animal body in the course of their activity combine with certain specific sites known as receptors. Histamine is a compound which is believed to act in this way but since the actions of histamine fall into more than one type, it is believed that there is more than one type of histamine receptor. The receptors involved in the type of action of histamine which is blocked by drugs commonly called "antihistamines" of mepyramine mepyamine is a typical example have been designated as H-1 histermine receptors (Ash and Schild. Brit. Jr. Pharmac, Chemother, 27, 427 (1966). The receptors involved in the type of action of histamine which is not blocked by "antihistamines" such as mepyramine have been designated as H-2 histamine receptors and harimamide has been defined as an H-2 histamine receptor inhibitor (Black et al. Nature 236, 385 (1972)). Thus H-2 histamine receptors may be defined as those distamine receptors which are not inhibited by mepyramine but are inhibited by burimamide.

Inhibitors of H-2 histamine receptors are of utility in inhibiting actions of histamine which are not inhibited by "antihistamines". They are useful, for example. as inhibitors of gastric acid secretion.

The compounds of this invention are H-2 histamine receptor inhibitors. These compounds are represented by the following general formula: ##STR1## wherein R₁ and R₂. which may be the same or different, each represent a grouping of the structure shown in Formula II:

    het -- (CH.sub.2).sub.m Z -- (CH.sub.2).sub.n --

FORMULA II

wherein Het is a nitrogen containing 5 or 6 membered heterocyclic ring such as imidazole, pyridine, thiazole. isothiazole, oxazole, isoxazole pyrazole, triazole, thiadiazole, pyrimidine, pyrazine or pyridazine which is optionally substituted by lower alkyl, hydroxyl, halogen or amino; Z is sulphur or a methylene group; m is 0, 1 or 2; n is 2 or 3 and the sum of m and n is 3,4, or when Y is other (than hydrogen, methyl, or hydroxyl, 2; X₁ and X₂, which may be the same or different, are each sulphur. CHNO₂ or NY wherein Y is hydrogen, hydroxy, lower alkyl cycno, CONH₂ or SO₂ R₃ ; R₃ is lower alkyl, substituted or unsubstituted aryl, preferably phenyl or tolyl, trifluoromethyl or amino; W is NH, and when X₁ and X₂ are NH W may also be sulphur; and q is an integer from 2 to 8; or a pharmaceutically acceptable acid addition salt thereof. It will be understood that the structure illustrated in Formula i is only one of several representations and that other tautomeric forms are also covered by the present invention.

Throughout the present specification and claims by the term `lower alkyl` we mean an alkyl group containing from 1 to 4 carbon atoms.

In a preferred group of compounds R₁ and R₂ are the same. R₁ and/or R₂ are preferably Het--CH₂ S(CH₂)₂ -- and it is particularly preferable that Het is imidazole optionally substituted by methyl or halogen; thiazole; or isothiazole or pyridine optionally substituted by methyl, hydroxyl or halogen. Likewise it is preferred that X₁ and X₂ to be same. Useful series of compounds are those wherein X₁ and X₂ are both sulphur, wherein X₁ and X₂ are both NY and Y is hydrogen or cyano, and wherein X₁ and X₂ are both CHNO₂.

It is preferred that q be from 2 to 4particularly 8. Examples of specific compounds falling within the scope of the present invention are:

1,2-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)thioureido]-ethane

1,3-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)thioureido]-propane

1,4-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)thioureido]-butane

1,3-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino] propane

1,3-bis-[N'-cyano-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino]propane

1,3-bis-[S-(N-2-(5-methyl-4-imidazolylmethylthio)ethyl)isothioureido]propane

The compounds of Formula I wherein W is NH. P₂ is the same as R₁, X₁ and X₂ are both X₃, X₃ being sulphur, CHNO₂, NH, NCN, or NSO₂ R₄, R₄ being lower alkyl, substituted or unsubstituted aryl, preferably phenyl or tolyl, or trifluoromethyl, may be prepared by treating an excess (preferably two equivalents) of a compound of Formula III:

    r.sub.1 nhe

formula iii

wherein E is hydrogen or ##STR2## X₃ being as defined above and A being lower alkyl, with a compound of Formula IV:

    bnh(ch.sub.2).sub.q NHB

formula iv

wherein both the groups B are hydrogen when E is ##STR3## and are ##STR4## when E is hydrogen, X₃ and A being as defined above.

Preferably this reaction is carried out in a solvent, such as ethanol, isopropanol or pyridine. When X₃ is NCN or NSO₂ R₄ the reaction may be modified by first adding a silver salt, such as silver nitrate, to the reactant bearing the ##STR5## function, removing the silver alkyl mercaptide which is formed and then adding the reacting amine.

Compounds of Formula III wherein E is ##STR6## and X₃ is sulphur may be prepared from an amine of formula R₁ NH₂ by successive reaction thereof with carbon disulphide and an alkylating agent, such as methyl iodide.

Compounds of Formula III wherein E is ##STR7## and X₃ is CHNO₂, NCN, or NSO₂ R₃ may be prepared by treating a compound of Formula V

    (as).sub.2 c ═ x.sub.3

formula v

wherein X₃ is CHNO₂, NCN, or NSO₂ R₄ and A is alkyl, with an equivalent amount of an amine of formula R₁ NH₂. This reaction is conveniently carried out in a solvent such as ethanol.

The compounds of Formula III wherein E is ##STR8## and X₃ is NH are conveniently prepared by alkylating a thiourea of formula R₁ NHCSNH₂. These thioureas may be prepared by treating an amine of formula R₁ NH₂ with benzoyl isothiocyanate, and hydrolysing the product under alkaline conditions.

The compounds of Formula IV wherein both the groups are ##STR9## may be prepared from the corresponding diamines by methods similar to these described above for the preparation of compounds of Formula III wherein Y is ##STR10##

Mild acid hydrolysis of the compounds of Formula I wherein X₁ and X₂ are both NCN yields the compounds of Formula I wherein X₁ and X₂ are both NCONH₂. Acid hydrolysis of the compounds of Formula I wherein X₁ and X₂ are both NCN yields the compounds of Formula I wherein X₁ and X₂ are both NH.

The compounds of Formula I wherein X₁ and X₂ are both NHSO₂ NH₂ may be prepared from the corresponding compounds of Formula I wherein W is NH and X₁ and X₂ are both NH by reaction of the latter compounds with N-piperidylsulphamide. This reaction is conveniently carried out in boiling ethanol.

The above methods of synthesis may be modified to produce those compounds wherein W = NH and X₁ and X₂ and/or R₁ and R₂ are different. In this case the starting material is conveniently the diamine of Formula IV, wherein both the groups B are hydrogen, which is first treated with a suitable reagent to form a mono-protected diamine of Formula VI:

    qnh(ch.sub.2).sub.q NH.sub.2

formula vi

wherein q has the above significance and Q is a suitable protecting group e.g., an acid labile protecting group such as benzoyl or formyl. Reaction of this compound with one equivalent of a compound of Formula III wherein E is ##STR11## gives the compound of Formula VII: ##STR12## wherein R₁, X₃, Q and q have the above significance. Treatment of this compound with acid followed by reaction with a substance of Formula VIII: ##STR13## wherein A, R₂ and X₂ have the above significance and R₂ and/or X₂ are not identical to R₁ and/or X₁ in Formula VII results in the required compound of Formula I wherein R₁ and R₂ and/or X₁ and X₂ are different. Alternatively, the amine of Formula VI may be converted into a compound of Formula IX: ##STR14## wherein Q, q, X₃ and S have the above significance, by the general methods described above for the preparation of compounds of Formula IV wherein E is ##STR15## Treatment of a compound of Formula IX with an amine of formula R₁ NH₂. R₁ being as defined above, gives a compound of Formula VII which may be converted into a compound of Formula I by successive treatment with acid and a compound of Formula VIII as described above.

It will be appreciated that the above processes for the production of compounds of Formula I wherein W is NH involve the reaction between a compound of Formula III and a compound of Formula X

    bnh(ch.sub.2).sub.q NHG

formula x

wherein B is hydrogen when E is ##STR16## and B is ##STR17## when E is hydrogen, A being lower alkyl and X₃ being sulphur, CHNO₂, NH, NCN or NSO₂ R₄. R₄ being lower alkyl, substituted or unsubstituted aryl or trifluoromethyl, q is as defined in Formula I and G is B or a group --CX₂ NHR₂ wherein X₂ and R₂ are as defined in Formula I.

The compounds of Formula I wherein X₁ and/or X₃ are NV and Y is hydroxy or lower alkyl may be prepared from the corresponding thiourea of Formula I wherein X₁, and/or X₂ is sulphur, and neither X₁ nor X₂ are NH by alkylating the thiourea, e.g., by treatment with hydrogen chloride in methanol or methyl iodide, and then treating the resulting compound with hydroxylamine or a lower alkylamine, respectively.

The compounds of Formula I wherein X₁ and/or X₂ are NCN may alternatively be prepared from the corresponding thiourea of Formula I wherein X₁ and/or X₂ is sulphur, and neither X₁ nor X₂ are NH, by alkylation and treatment of the product with cyanamide and a strong base such as potassium t-butoxide.

The compounds of Formula I wherein X₁ or X₂ are N, CN may also be prepared from the corresponding compounds of Formula I wherein X₁ or X₂ are sulphur by reaction of the latter with a heavy metal salt of cyanamide such as lead, mercury or cadmium cyanamide in a solvent such as acetonitrile and/or dimethylformamide.

The compounds of Formula I wherein W is sulphur and X₁ and X₂ are both NH may be prepared by alkylating a thiourea of Formula R₁ NHCSNH₂ wherein R₁ is as defined in Formula I with a dihalo compound of formula Hal--(CH₂)_(q) --Hal, wherein Hal represents chlorine, bromine or iodine. Preferably the reaction is carried out on an acid addition salt of the thiourea, Hal is bromine and the reaction is carried out in a suitable solvent such as ethanol.

The compounds of Formula I are inhibitors of H-2 histamine receptors, that is they are inhibitors of the actions of histamine which are not blocked by "antihistamines" such as mepyramine but are blocked by burimamide. For example, the compounds of this invention have been found to inhibit selectively the histamine-stimulated secretion of gastric acid from the lumen-perfused stomachs of rats anaesthetized with urethane, at doses of from 0.5 to 256 micromoles per kilogram intravenously. This procedure is described in the above mentioned paper of Ash and Schild. Also, the activity of these compounds as H-2 histamine receptor inhibitors is demonstrated by their antagonism to other actions of histamine which, according to the above mentioned paper of Ash and Schild, are not mediated by H-1 histamine receptors. For example, the H-2 histamine receptor inhibitory activity of the compounds of this invention is demonstrated by antagonism of the actions of histamine in stimulating isolated guinea pig atrium and inhibiting contractions in the isolated rat uterus.

The compounds of this invention inhibit the secretion of gastric acid stimulated by pentagastrin or by food. The level of activity found for the compounds of the present invention is illustrated by the effective dose range in the anaesthetised rat, as mentioned above of from 0.5 to 256 micromoles per kilogram, intravenously. Many of the compounds of the present invention produce a 50% inhibition in this test at a dose of from 1 to 10 micromoles per kilogram.

For therapeutic use, the pharmacologically active compounds of the present invention will normally be administered as a pharmaceutical composition comprising as the or an essential active ingredient at least one such compound in the basic form or in the form of an addition salt with a pharmaceutically acceptable acid and in association with a pharmaceutical carrier therefor. Such addition salts include those with hydrochloric, hydrobromic, hydriodic, sulphuric and maleic acids and may conveniently be formed from the corresponding bases of Formula I by standard procedures, for example by treating the base with an acid in a lower alkanol or by the use of ion exchange resins to form the required salt either directly from the base or from a different addition salt. Pharmaceutical compositions comprising a pharmaceutical carrier and a compound of Formula I or a pharmaceutically acceptable acid addition salt thereof and methods of inhibiting H-2 histamine receptors which comprise administering a compound of Formula I or a pharmaceutically acceptable acid addition salt thereof are also objects of this invention. The pharmaceutical carrier employed may be, for example, either a solid or liquid. Exemplary of solid carriers are lactose, terra alba, sucrose, talc, gelatin, agar, pectin, acacia, magnesium stearate, stearic acid and the like. Exemplary of liquid carriers are syrup, peanut oil, olive oil, water and the like.

A wide variety of pharmaceutical forms can be employed. Thus, if a solid carrier is used, the preparation can be tableted, placed in a hard gelatin capsule in powder or pellet form, or in the form of a troche or lozenge. The amount of solid carrier will vary widely but preferably will be from sheet 25 mg to about 1 g. If a liquid carrier is used, the preparation may be in the form of a syrup, emulsion, soft gelatin capsule, sterile injectable liquid such as in an ampoule, or an aqueous or non-aqueous liquid suspension.

The pharmaceutical compositions are prepared by conventional techniques, involving procedures such as mixing, granulatinc and compressing or dissolving the ingredients as appropriate to the desired preparation.

The active ingredient will be present in the compositions in an effective amount to inhibit H-2 histamine receptors. The route of administering may be orally or parenterally. Preferably, each dosage unit will contain the active ingredient in an amount of from about 50 mg to about 250 mg. The active ingredient will preferably be administered in equal doses one to six times per day. The daily dosage regimen will preferably be from about 150 mg to about 1500 mg. Other pharmacologically active compounds may in certain cases be included in the composition. Advantageously the composition will be made up in a dosage unit form appropriate to the desired mode of administration, for example as a tablet, capsule or injectable solution.

The invention is illustrated but in no way limited by the following examples wherein all temperatures are in degrees Centigrade:

EXAMPLE 1 1,2-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)thioreido]ethane.

(a) A solution of 4-methyl-5-((2-aminoethyl)thiomethyl)imidazole (10.2 g) in ethanol (75 ml) was added slowly, with stirring, to carbon disulphide (200 ml). The mixture was set aside overnight at room temperature and the solid formed was collected and recrystallised from aqueous isopropyl alcohol to afford N-[2-((5-methyl-4-imidazolyl)methylthio)ethyl]dithiocarbamic acid (9.8 g)., m.p. 127-129°.

(Found: C, 38.6; H, 5.5; N, 16.7; C₈ H₁₃ N₃ S₃. requires: C, 38.8; H, 5.3; N, 17.0%).

(b) Methyl iodide (4.0 g) was added to a suspension of the dithiocarbamic acid (7.0 g) in methanol (100 ml). After stirring at room temperature for 1.5 hours, a solution was obtained. Concentration followed by recrystallisation of the residue from isopropyl alcohol-ether gave S-methyl-N-[2-((5-methyl-4-imidazolyl)methylthio)ethyl]-dithiocarbamate hydriodide (8.6 g), m.p. 167-169°.

(Found: C, 27.7; H, 4.0; N, 10.8; I, 32.9; C₉ H₁₅ N₃ S₃.HI. requires: C, 27.8; H, 4.1; N, 10.8; I, 32.6%).

(c) A solution of the above hydriodide (5.5 g) in absolute ethanol (60 ml) was added to a solution of sodium (0.325 g) in ethanol (100 ml). Following filtration, a solution of 1,2-diaminoethane (0.424 g) in ethanol (30 ml) was added to the filtrate which was heated under reflux for 24 hours. Following concentration, the residual oil was purified by repeated reprecipation from isopropanol with water and from isopropanol with ether. Finally chromatographic purification on a column of silica gel with ethyl acetate-ethanol (3:1) as eluant and final precipitation from isopropanol-ether gave the title compound as a colourless low melting solid, containing approximately 4.5% diethyl ether. The NMR spectrum of a solution in ² H₆ dimethyl sulphoxide, recorded at 60 mHZ showed the following resonances:

    __________________________________________________________________________     --NH--CS--NH--: multiplet at δ7.7                                                                 integral, 6.0 protons:                                                         calculated, 6.0 protons.                              imidazole-2-H: singlet at δ7.48                                          imidazole-CH.sub.2 --: singlet, at δ3.68                                                          integral, 12.4 protons:                                                        calculated, 12.0 protons.                             --CH.sub.2 --NH--CS--NH--CH.sub.2 : multiplet at δ3.5                    --CH.sub.2 CH.sub.2 S--: multiplet, at δ2.62                                                      integral could not be                                                          measured                                              imidazole-CH.sub.3 : singlet, at δ2.13 :                                                          the integral was used as                                                       the internal standard,                                                         equal to 6.0 protons.                                 __________________________________________________________________________

The spectrum also showed the presence of 4.5% w/w diethyl ether.

(Found: C, 45.6: H, 6.7; C₁₈ H₃₀ N₈ S₄ + 4.5%. C₄ H₁₀ O. requires: C, 45.3; H, 6.5%).

EXAMPLE 2 1,3-bis-[N'-(2-(5-methyl-4-imidazolyl methylthio)ethyl)thioureido]propane

S-Methyl-N'-[2-(5-methyl-4-imidazolyl)methylthio)ethyl]dithiocarbamate hydriodide (7.8 g) was converted into the free base with sodium (0.46 g) in ethanol. Reaction with 1,3-diaminopropane (0.74 g) and purification by the method described in Example 1 gave the product which was further purified by successive treatment of a solution in methanol-water with cationic and anionic exchange resins. Following precipitation from isopropanol-ether, the title compound was obtained as a colourless low melting solid containing approximately 4.5% diethyl ether.

The NMR spectrum of a solution in ² H₆ dimethyl sulphoxide recorded at 60 mHZ showed the following resonances.

    __________________________________________________________________________     --NH--CS--NH--; triplet δ7.62                                                                     integral, 7.0 protons;                                                         calculated 6.0 protoms.                               imidazole-2H: singlet δ7.42                                              imidazole-CH.sub.2 : singlet,δ3.67                                                                integral 12.0 protons(including                                                H.sub.2 O in NMR solvent):calculated                  CH.sub.2 NH--CSNH--CH.sub.2 : multiplet, δ3.5                                                     12.0.                                                 CH.sub.2 --CH.sub.2 --S: triplet δ2.60                                                            integral 5.0 protons(including                                                 DMSO-d.sub.5)-calculated 4.0.                         imidazole-CH.sub.3 : singlet δ2.13                                                                The integral was used as the                                                   internal standard, equal to                                                    6.0 protons.                                          CH.sub.2 CH.sub.2 CH.sub.2 : multiplet δ1.71                                                      integral 2.0 protons;                                                          calculated 2.0 protons.                               __________________________________________________________________________

The spectrum also showed the presence of 4.5% weight/weight diethyl ether.

(Found: N, 21.7; S, 24.6; C₁₉ H₃₂ N₈ S₄ + 4.5% C₄ H₁₀ O. requires: N, 21.4; S, 24.5%).

EXAMPLE 3 1,4-bis-[N'-(2-(5-Methyl-4-imidazolylmethylthio)ethyl)thioureido]butane

S-Methyl-N'-[2-(5-methyl-4-imidazolyl)methylthio)ethyl]dithiocarbamate hydriodide (5.5 g) was converted into the free base with sodium in ethanol. Reaction with 1,4-diaminobutane (0.63 g) and subsequent purification by the method described in Example 1 afforded the title compound as a low-melting colourless solid containing approximately 5.9% diethyl ether.

The NMR spectrum of a solution in ² H₆ dimethyl sulphoxide recorded at 60 mHZ showed the following resonances.

    __________________________________________________________________________     --NH--CS--NH--: multiplet, δ7.6                                                             integral 5.8 protons;                                                          calculated, 6.0 protons.                                    imidazole-2H: singlet, δ7.47                                             imidazole-CH.sub. 2 : singlet, δ3.69                                                        integral 12.6 protons:                                                         calculated, 12.0 protons.                                   CH.sub.2 CH.sub.2 N--: multiplet, δ3.5                                   CH.sub.2 CH.sub.2 S: triplet, δ2.63                                                         The integral could not                                                         be measured.                                                CH.sub.3 -Imidazole: singlet, δ2.15:                                                        The integral was used as                                                       the internal standard                                                          equal to 6.0 protons.                                       CH.sub.2 --(CH.sub.2).sub.2 --CH.sub.2 : multiplet, δ1.5                                    integral 4.2 protons                                                           calculated 4.0 protons.                                     __________________________________________________________________________

The spectrum also showed the presence of 5.9% weight/weight diethyl ether.

(Found: C, 47.6; H, 7.2; C₂₀ H₃₄ N₈ S₄ + 5.9%. C₄ H₁₀ O requires: C, 47.7; H, 7.1%).

EXAMPLE 4 1,5-bis-[N'-(2-(5-Methyl-4-imidazolylmethylthio)ethyl]thioureido)pentane

The reaction of S-methyl-N'-[2-(5-methyl-4-imidazolyl)methylthio)ethyl]dithiocarbamate with 1,5-diaminopentane by the method described in Example 1 gave the title compound as an amorphous powder which contained residual ether and water.

(Found: C, 47.5; H, 7.2; N, 19.9; S, 23.3; C₂₁ H₃₆ N₈ S₄ 2% C₄ H₁₀ O + 2% H₂ O requires: C, 47.1; H, 7.1; N, 20.3; S, 23.3%).

The NMR spectrum of a solution in ² H₆ dimethyl sulphoxide recorded at 60 mHZ showed the following resonances.

    __________________________________________________________________________     --NH--CS--NH--: multiplet, 435-465 H.sub.Z                                                               integral 5.3 protons                                                           calculated, 6.0 protons                              imidazole-2H: singlet, δ7.47                                             imidazole-CH.sub.2 : singlet, δ3.68                                                                integral 12.3 protons                                                          calculated 12.0 protons                              CH.sub.2 CH.sub.2 S+CH.sub.2 CH.sub.2 N: multiplet, 185-235 H.sub.Z            CH.sub.2 --CH.sub.2 --S; multiplet, 140-175 H.sub.Z                                                      integral 4.5 protons                                                           (including DMSO-d.sub.5)                                                       calculated 4 protons                                 CH.sub.3 Imidazole: singlet, δ2.15:                                                                The integral was used                                                          as the internal                                                                standard equal to                                                              6 protons.                                           CH.sub.2 (CH.sub.2 --CH.sub.2).sub.2 NH multiplet, 70-110                                                Integral 5.3 protons                                                           calculated 6.0 protons                               __________________________________________________________________________

EXAMPLE 5 1,3-bis[N'-(2-(5-Methyl-4-imidazolylmethylthio)ethyl)guanidino]propane

(i) A solution of N-[2-((5-methyl-4-imidazolyl)methylthio)ethyl] thiourea (2.29 g) and methyl iodide (1.56 g) in methanol (5ml) was kept at room temperature for 18 hours affording S-methyl-N-[2-((5-methyl-4-imidazolyl)methylthio)ethyl]thiouronium iodide (2.3 g). m.p. 128°-131°. The iodide was converted into the corresponding sulphate by ion-exchange on an ion-exchange resin (IRA 401) in the sulphate form.

(ii) 1,3-Diaminopropane (0.37 g) was added to a solution of S-methyl-N-[2-((5-methyl-4-imidazolyl)methylthio)ethyl]thiouronium sulphate (2.93g) in water (10 ml) and the mixture was heated under reflux for 2 hours. Following concentration the residue was converted into the picrate with an aqueous solution of sodium picrate. Recrystallisation from ethanol afforded the title compound as the dipicrate (1.1 g) m.p. 114°-6°.

(Found: C, 40.3; H, 4.2; N, 23.7; S, 6.9; C₁₉ H₃₆ N₁₀ S₂.2 C₆ H₃ N₃ O₇. requires: C, 40.3; H, 4.4; N, 24.2; S, 6.9%.

The dipicrate was dissolved in aqueous methanol and treated with ion-exchange resin IRA 400 (Cl⁻) to afford the dihydrochloride

(Found: Cl, 12.8% C₁₉ H₃₆ N₁₀ S₂. 2HCl requires: Cl, 13.1%).

EXAMPLE 6 1,2-bis-[N'-(2-(5-Methyl-4-imidazolylmethylthio)ethyl)guanidino] ethane

The reaction of 1,2-diaminoethane (0.60 g) with S-methyl-N-[2-((5-methyl-4-imidazolyl)methylthio)ethyl]thiouronium sulphate (5.86 g) by the method described in Example 5 afforded the title compound which was isolated as the dipicrate (3.5 g). m.p. 201°-203°.

(Found: C., 39.5; H, 4.3; N, 24.2; S, 6.9; C₁₈ N₃₄ N₁₀ S₂. 2 C₆ H₃ N₃ O₇ requires: C, 39.6; H, 4.2; N, 24.6; S, 7.0%).

EXAMPLE 7 1,5-bis[N'-(2-(5-Methyl-4-imidazolylethylthio)ethyl)guanidino] pentane

The reaction of 1,5-diaminopentane (0.43 g) with S-methyl-N-[2-((5-methyl-4-imidazolyl)methylthio)ethyl]thiouronium sulphate (2.52 g) by the method described in Example 5 afforded the title compound which was isolated as the dipicrate (1.8 g) m.p. 115- 120°.

EXAMPLE 8 1,3-bis-[- N'-Cyano-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino] propane

(a) A mixture of 1,3-bis-[N-cyano-S-methyl-isothiouredo]propane (1.67 g) and 5-methyl-4-(2-aminoethyl)imidazole (2.36 g) in anhydrous pyridine (40 ml) was heated under reflux for 8 hours. Following concentration and trituration with acetonitrile-water (2:1) the product was chromatographed on a column of silica with elution by a mixture of chloroform (85 parts) and methanolic ammonia (15 parts) to yield the title compound.

The NMR spectrum of a solution in ² H₆ dimethyl sulphoxide showed the following resonances.

imidazole-2H; Singlet, δ 7.56

N-h; multiplet, δ 7.22

imidazole-CH₂ ; singlet, δ 3.68

Ch₂ ch₂ nh; multiplet, δ 3.25 NH;

Ch₂ ch₂ s; multiplet, δ 2.65

Ch₃ -imidazole; singlet,δ 2.16

Ch₂ ch₂ ch₂ ; multiplet, δ 1.75

(b) Lead cyanamide (3.0 g) was added to 1,3 -bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)thioureido] propane (2.5 g) in acetonitrile. Dimethylformamide was added and the mixture was stirred and boiled under reflux for 24 hours. The mixture was filtered, concentrated and purified by chromatography to give the title compound.

(c) A mixture of 1,3-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)thioureido)]propane (10.3 g) 55% hydriodic acid (12.2 ml) methyl iodide (5.3 ml) and methanol was boiled under reflux for 4 hours and, evaporated to dryness to give 1,3-bis-[S-methyl-N'-(2-(5-methyl-4-imidazolylmethylthio)-ethyl)isothioureido)]propane tetrahydriodide. This intermediate (2.05 g) was treated with potassium t-butoxide (1.5 g) and cyanamide (0.5 g) in anhydrous t-butanol and the mixture was boiled under reflux overnight, filtered, and purified by chromatography to give the title product.

EXAMPLE 9 1,2-bis-[S-(N-2-(5-Methyl-4-imidazolylmethylthio)ethyl)isothioureido] ethane tetrahydrobromide

A solution of N-[2-(5-methyl-4-imidazolyl)methylthio)ethyl] thiourea (3.45 g) in isopropyl alcohol (25 ml) was cooled and 48% aqueous hydrobromic acid (2.54 g) added. The hydrobromide salt was precipitated with excess ether and dissolved in ethanol (25 ml). 1,2-Dibromoethane (1.5 g) was added and the solution obtained was heated under reflux for 24 hours. Concentration and crystallisation from methanol-isopropyl alcohol afforded the title compound (2.2 g) m.p. 215-217°.

(Found: C., 26.7; H, 4.1; N, 13.8; S, 15.8; Br, 39.6; C₁₈ H₃₀ N₈ S₄. 4 HBr requires: C, 26.7; H, 4.2; N, 13.8; S, 15.8; Br, 39.4%).

EXAMPLE 10 1,3-bis-[5-(N-2-(5-Methyl-4-imidazolylmethylthio)ethylisothioureido] propane

The reaction of N-[2-(5-methyl-4-imidazolyl)methylthio)ethyl]thiourea hydrobromide (from 3.45 g of the thiourea) with 1,3-dibromopropane by the method described in Example 9 afforded the title compound which was isolated as its tetrapicrolonic acid salt (4.75 g), m.p. 165-167° (from nitromethane-ethanol).

(Found: C, 45.2; H, 4.3; N, 21.5; S, 7.8%. C₁₉ H₃₂ N₆ S₄. 4C₁₀ H₈ N₄ O₅ requires: C, 45.5; H, 4.1; N, 21.6; S, 8.2%).

The tetrapierolonate salt was suspended in aqueous methanol and treated with ion-exchange resin IRA 401 (Cl⁻ form) and the suspension stirred for 3 hours. Concentration afforded the tetrahydrochloride (0.9 g), m.p. approx.110°

(Found: C, 35.1; H, 6.0: C₁₉ H₃₂ N₈ S₄. 4 HCl requires: C, 35.3 H, 5.9%).

EXAMPLE 11 1,4-bis-[S-(N-2-(5-Methyl-4-imidazolylmethylthio)ethyl)isothioureido] butane tetrahydrobromide

The reacton of N-[2-(4-methyl-5-imidazolyl)methylthio)ethyl]thiourea hydrobromide (from 3.45 g of the thiourea) with 1,4-dibromobutane (1.62 g) by the method described in Example 9 afforded the title compound (3.8 g), m.p. 185-187° (from ethanol)

(Found: C, 28.7; H, 4.6; N, 13.4; Br, 38.2; S, 15.1; C₂₀ H₃₄ N₈ S₄. 4 HBr requires: C, 28.7; N, 4.6; N, 13.4; S, 38.1; S, 15.3%).

EXAMPLE 12

When 1,8-diaminooctane is substituted for 1,2-diaminoethane in the procedure of Example 1(c), 1,8-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)thioureido]octane is produced. When 1,8-diaminooctane is substituted for 1,3-diaminopropane in the procedure of Example 5(ii), 1,8-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino]octane is produced.

When 1,6-diaminohexane is substituted for 1,2-diaminoethane in the procedure of Example 1(c), 1,6-bis-['-(2-(5-methyl-4-imidazolylmethylthio)ethyl)thioureido)]hexane is produced. When 1,6-diaminohexane is substituted for 1,3-diaminopropane in the procedure of Example 5(ii), 1,6-bis-[N'-(2-(5-methyl-4imidazolylmethylthio)ethyl)guanidino]hexane is produced.

EXAMPLE 13

When 1,6-dibromohexane or 1,8-dibromooctane are substituted for 1,2-dibromoethane in the procedure of Example 9 the products are 1,6-bis-[S-(N-2-(5-methyl-4-imidazolylmethylthio)ethyl)isothioureido] hexane and 1,8-bis-[S-(N-2-(5-methyl-4-imidazolylmethylthio)ethyl)isothioureido]octane, respectively.

EXAMPLE 14

Reaction of 4-methyl-5-((2-aminoethyl)thiomethyl)imidazole with

(a) N-methanesulphonyliminodithiocarbonic acid dimethyl ester

(b) N-p-toluenesulphonyliminodithiocarbonic acid dimethyl ester

(c) N-benzenesulphonyliminodithiocarbonic acid dimethyl ester

(d) N-trifluoromethanesulphonyliminodithiocarbonic acid dimethyl ester in ethanol at room temperature gave the corresponding S-methyl-N-[2-((5-methyl-4-imidazolyl)methyltho)ethyl]-N'-sulphonylthiouronium derivatives which were treated with 1,3-diaminopropane according to the general procedure of Example 5(ii) to give

(a) 1,3-bis-[N'-methanesulphonyl-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino]propane

(b) 1,3-bis-[N'-toluenesulphonyl-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)-guanidino]propane

(c) 1,3-bis-[N'-benzenesulphonyl-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)-guanidino]propane

(d) 1,3-bis-[N'-trifluoromethanesulphonyl-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)-guanidino]propane

EXAMPLE 15 1,3-bis-[N'-Sulphamyl-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino] propane

1,3-bis-[N'-(2-(5-Methyl-4-imidazolylmethylthio)ethyl)guanidino]propane dihydrochloride (2.7 g) was added to a solution of sodium (0.46 g) in ethanol (50 ml) and the mixture was warmed and stirred for 0.5 hours, cooled and filtered, N-Piperidylsulphamide (1.64 g) was added to the filtrate which was heated under reflux for 24 hours. The mixture was concentrated and purified by chromatography to give the title compound.

EXAMPLE 16 1,3-bis-[N'-Hydroxy-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino] propane

(a) Dry hydrogen chloride was bubbled through a solution of 1,3-bis-[N'-(2-(5-methyl-4-imidazolylmethylthio)ethylthioureido] propane in methanol at 80° for 12 hours, and the solvent was removed to give 1,3-bis[S-methyl-N'-(2-(5-methyl-4-imidazolymethylthio)ethyl)isothioureido]propane tetrahydrochloride.

(b) The bis-isothiourea prepared above was treated with hydroxylamine hydrochloride and potassium hydrogen carbonate in dry dimethylformamide at 85° under an atmosphere of nitrogen to yield the title product.

EXAMPLE 17 1,3-bis-[N'-Methyl-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino] propane

1,3-bis-[S-Methyl-N'-(2-(5-methyl-4-imidazolylmethylthio)ethyl)isothioureido] propane tetrahydrochloride was heated with methylamine in methanol to give the title product.

EXAMPLE 18

Substitution of

(a) 4-bromo-5-[(2-aminoethyl)thiomethyl]imidazole

(b) 4-[(2-aminoethyl)thiomethyl]imidazole

(c) 2-[(2-aminoethyl)thiomethyl]thiazole

(d) 3-[(2-aminoethyl)thiomethyl]isothiazole

(e) 3-chloro-2-[(2-aminoethyl)thiomethyl]pyridine

(f) 3-hydroxy-2-[(2-aminoethyl)thiomethyl]pyridine

(g) 3-methyl-2-[(2-aminoethyl)thiomethyl]pyridine

for 4-methyl-5-((2-aminoethyl)thiomethyl)imidazole in the procedure of Example 1(a) followed by treatment of the product according to the general procedure of Examples 1(b) and 2 gave

(a) 1,3-bis[N'-(2-(5-bromo-4-imidazolylmethylthio)ethyl)thioureido]propane

(b) 1,3-bis[N'-(2-(4-imidazolylmethylthio)ethyl)thioureido]propane

(c) 1,3-bis[N'-(2-(2-thiazolylmethylthio)ethyl)thioureido]propane

(d) 1,3-bis[N'-(2-(3-isothiazolylmethylthio)ethyl)thioureido]propane

(e) 1,3-bis[N'-(2-(3-chloro-2-pyridylmethylthio)ethyl)thioureido]propane

(f) 1,3-bis[N'-(2-(3-hydroxy-2-pyridylmethylthio)ethyl)thioureido]propane

EXAMPLE 19

Substitution of the following amines:

(a) 2-[2-aminopropylthio]oxazole

(b) 3-[(2-aminoethyl)thiomethyl]isoxazole

(c) 3-[(2-aminoethyl)thiomethyl]pyrazole

(d) 3-[(2-aminoethyl)thiomethyl]-1,2,4-triazole

(e) 5-amino-2-[(2-aminoethyl)thiomethyl]-1,3,4-thiadiazole

(f) 2-[(2-aminoethyl)thiomethyl]pyrimidine

(g) 2-[(2-aminoethyl)thiomethyl]pyrazine

(h) 3-[(2-aminoethyl)thiomethyl]pyridazine

(i) 1-methyl-2-[(2-aminoethyl)thiomethyl]imidazole

(j) 2-[(2-aminoethyl)thiomethyl]imidazole

for 4-methyl-5-((2-aminoethyl)thiomethyl)imidazole in the procedure of Example 1(a) followed by treatment of the products according to the general procedure of Examples 1(b) and 2 results in the production of the following products

(a) 1,3-bis[N'-(2-(2-oxazolylthio)propyl)thioureido]propane

(b) 1,3-bis[N'-(2-(3-isoxazolylmethylthio)ethyl)thioureido]propane

(c) 1,3-bis[N'-(2-(3-pyrazolylmethylthio)ethyl)thioureido]propane

(d) 1,3-bis[N-(2-(3-(1,2,4-triazolyl)methylthio)ethyl)thioureido]propane

(e) 1,3-bis[N-(2-(5-amino-2-(1,3,4-thiadiazolyl)methylthio)ethyl)thioureido]propane

(f) 1,3-bis[N-(2-(2-pyrimidylmethylthio)ethyl)thioureido]propane

(g) 1,3-bis[N'-(2-(2-pyrazolylmethylthio)ethyl)thioureido]propane

(h) 1,3-bis[N'-(2 -(3-pyridazolylmethylthio)ethyl)thioureido]propane

(i) 1,3-bis[N'-(2-(1-methyl-2-imidazolylmethylthio)ethyl)thioureido]propane

(j) 1,3-bis[N'-(2-(2-imidazolylmethylthio)ethyl)thioureido]propane

EXAMPLE 20

(a) (i) A solution of 4-(2-aminoethyl)thiomethyl)imidazole (6.0 g) and benzoyl isothiocyanate (6.0 g) in chloroform (150 ml) was heated under reflux for one hour. Concentration followed by recrystallisation from ethyl acetate-isopropyl acetate afforded N-benzoyl-N'-(2-(4-imidazolylmethylthio) ethyl)thiourea (7.5 g). An analytically pure sample (from aqueous isopropyl alcohol) had m.p. 126-128°.

(ii) The benzoyl thiourea (6.0 g) was added to a solution of potassium carbonate (1.4 g) in water (80 ml) at 60°. The solution was maintained at this temperature for one hour, concentrated to low bulk and acidified with hydrochloric acid. Benzoic acid was removed by filtration and the filtrate was basified with potassium carbonate and concentrated under reduced pressure. Following extraction with isopropyl alcohol and concentration, the product was crystallised from isopropyl acetate. Recrystallisation from water gave N-(2-(4-imidazolylmethylthio)ethyl)thiourea (2.5 g) m.p. 135-7°.

Found: C., 38.9; H, 5.5; N, 26.1; S, 29.6; C₇ H₁₂ N₄ S₂ requires: C, 38.9; H, 5.6; N, 25.9; S, 29.6%).

(b) Substitution of

(a) 4-bromo-5-[(2-aminoethyl)thiomethyl)imidazole

(b) 4-[(2-aminoethyl)thiomethyl]imidazole

(c) 2-[(2-aminoethyl)thiomethyl]thiazole

(d) 3-[(2-aminoethyl)thiomethyl]isothiazole

(e) 3-chloro-2-[(2-aminoethyl)thiomethyl]pyridine

(f) 3-hydroxy-2-[(2-aminoethyl)thiomethyl]pyridine

(g) 3-methyl-2-[(2-aminoethyl)thiomethyl]pyridine

for 4-(2-aminoethyl)thiomethyl)imidazole in the above procedure and treatment of the products according to the general procedure of Example 5 gives

(a) 1,3-bis[N'-(2-(5-bromo-4-imidazolylmethylthio)ethyl)guanidino]propane

(b) 1,3-bis[N'-(2-(4-imidazolylmethylthio)ethyl)guanidino]propane

(c) 1,3-bis[N'-2-(2-thiazolylmethylthio)ethyl)guanidino]propane

(d) 1,3-bis[N'-(2-(3-isothiazolylmethylthio)ethyl)guanidino]propane

(e) 1,3-[N'-(2-(3-chloro-2-pyridylmethylthio)ethyl)guanidino]propane

(f) 1,3-bis[N'-(2-(3-hydroxy-2-pyridylmethylthio)ethyl)guanidino]propane

EXAMPLE 21

Treatment of

(a) 2-[2-aminopropylthio]oxazole

(b) 3-[(2-aminoethyl)thiomethyl]isoxazole

(c) 3-[(2-aminoethyl)thiomethyl]pyrazole

(d) 3-[(2-aminoethyl)thiomethyl]-1,2,4-triazole

(e) 2-[(3-aminopropylthio]pyrimidine

(f) 2-[(2-aminoethyl)thiomethyl]pyrazine

(g) 3-[(2-aminoethyl)thiomethyl]pyridazine

(h) 1-methyl-2-[(2-aminoethyl)thiomethyl]imidazole

(i) 2-[(2-aminoethyl)thiomethyl]imidazole

according to the general procedure of Example 20 gives

(a) 1,3-bis[N'-(2-(2-oxazolylthio)propyl)guanidino]propane

(b) 1,3-bis[N'-(2-(3-isoxazolylmethylthio)ethyl)guanidino]ppropane

(c) 1,3-bis[N'-(2-(3-pyrazolylmethylthio)ethyl)guanidino]propane

(d) 1,3-bis[N-(2-(3-(1,2,4-triazolyl)methylthio)ethyl)guanidino]propane

(e) 1,3-bis[N-(3-(2-pyrimidylthio)propyl)guanidino]propane

(f) 1,3-bis[N'-(2-(3-pyrazolylmethylthio)ethyl)guanidino]propane

(g) 1,3-bis[N'-(2-(3-pyridizylmethylthio)ethyl)guanidino]propane

(h) 1,3-bis[N'-(2-(1-methyl-2-imidazolylmethylthio)ethyl)guanidino]propane

(i) 1,3-bis[N'-(2-(2-imidazolylmethylthio)ethyl)guanidino]propane

EXAMPLE 22

Substitution of

(a) 4-(4-aminobutyl)imidazole

(b) 4-(4-aminobutyl)-5-methylimidazole

(c) 4-(4-aminobutyl)-5-bromoimidazole

(d) 4-(4-aminobutyl)thiazole

for 4-methyl-5-(2-aminoethyl)thiomethyl)imidazole in the procedure of Example 1(a) followed by treatment of the product according to the general procedure of Examples 1(b) and 2 gave

(a) 1,3-bis-[N'-4-(4-imidazolylbutyl)thioureido]propane

(b) 1,3-bis-[N'-4-(5-methyl-4-imidazolylbutyl)thioureido]propane

(c) 1,3-bis-[N'-4-(5-bromo-4-imidazolylbutyl)thioureido]propane

(d) 1,3-bis-[N'-4-(4-thiazolylbutyl)thioureido]propane

EXAMPLE 23

Treatment of

(a) 4-(4-aminobutyl)imidazole

(b) 4-(4-aminobutyl)-5-methylimidazole

(c) 4-(4-aminobutyl)-5-bromoimidazole

(d) 4-(4-aminobutyl)thiazole

according to the general procedure of Example 20 gives

(a) 1,3-bis-[N'-4-(4-imidazolylbutyl)guanidino]propane

(b) 1,3-bis-[N'-4-(5-methyl-4-imidazolylbutyl)quanidino]propane

(c) 1,3-bis-[N'-4-(5-bromo-4-imidazolylbutyl)guanidino]propane

(d) 1,3-bis-[N'-4-(4-thiazolylbutyl)guanidino]propane

EXAMPLE 24 1-[N'-(2-(5-Methyl-4-imidazolylmethylthio)ethyl)guanidino]-3-[N'-(2-(2-thiazolylmethylthio)ethyl)thioureido]propane

(a) (i) 3-Benzoylaminopropylamine was treated successively with carbon disulphide and methyl iodide according to the general procedure of Example 1(a)(b) to give S-methyl-N-(3-benzoylaminopropyl)dithiocarbamate hydriodide

(ii) The above hydriodide was treated with one equivalent of sodium ethoxide and 2[(2-aminoethyl)thiomethyl]thiazole, and the product was hydrolysed with acid to give N-(3-aminopropyl)-N'-(2-(2-thiazolylmethylthio)ethyl)thiourea

(iii) The above thiourea was heated under reflux for 2 hours with an aqueous solution of S-methyl-N-[2-((5-methyl-4-imidazolyl)methylthio)ethyl]thiouronium sulphate in water. The mixture was concentrated and purified by chromatography to give the title compound.

(b) (i) 2-[(2-Aminoethyl)thiomethyl]thiazole was successively treated with carbon disulphide and methyl iodide according to the general procedure of Example 1(a)(b) to give S-methyl-N-[2-(2-thiazolylmethylthio)ethyl]dithiocarbamate hydriodide.

(ii) The above hydriodide was treated with one equivalent of sodium ethoxide and 3-benzoylaminopropylamine and the product was hydrolysed with acid, and subjected to the procedure (a) (iii) above, to give the title compound.

EXAMPLE 25 1,3-bis-[N'-(2-(4-imidazolylethylthio)ethyl)guanidino]propane

When 4-[2-(2-aminoethyl)thioethyl]imidazole is subjected to the general procedure of Example 20 the title compound is produced.

EXAMPLE 26 1,3-bis-[N'-Carbamoyl-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino]propane

Treatment of 1,3-bis-[N'-cyano-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidino]propane with dilute hydrochloric acid at 40° yielded the title product.

EXAMPLE 27 1,3-bis-[1-[2-((5-Methyl-4-imidazolyl)methylthio)ethylamino]-2-nitrovinylamino]propane

A solution of 1-nitro-2-methylthio-2-[2-(5-methyl-4-imidazolyl)methylthio)ethylamino]ethylene (2.0 g) and 1,3-diaminopropane (0.26 g) in ethanol (10 ml) was heated under reflux for 2 hours. The product was purified on an ion-exchange resin (GC 50 (H⁺)), by elution with 0.012 N hydrochloric acid and finally chromatographed on a column of silica gel to yield the title compound.

EXAMPLE 28 1-[1-(2-((5-Methyl-4-imidazolyl)methylthio)ethylamino)-2-nitrovinylamino]-3-[N'-cyano-N"-(2-(2-pyridylmethylthio)ethyl)guanidino]propane

1-Nitro-2-methylthio-2-[2-((5-methyl-4-imidazolyl)methylthio)ethylamino]ethylene was reacted with 3-benzoylaminopropylamine and the product was hydrolysed under acidic conditions and reacted with N-cyano-N'-[2-(2-pyridylmethylthio)ethyl]-S-methylisothiourea to give the title compound.

EXAMPLE 29

    ______________________________________                                         Ingredients              Amounts                                               ______________________________________                                         1,3-bis-[N'-(2-(5-Methyl-4-imidazolyl-                                         methylthio)ethyl)guanidino]propane                                                                      150 mg.                                               dihydrochloride                                                                Sucrose                  75 mg.                                                Starch                   25 mg.                                                Talc                     5 mg.                                                 Stearic Acid             2 mg.                                                 ______________________________________                                    

The ingredients are screened, mixed and filled into a hard gelatin capsule.

EXAMPLE 30

    ______________________________________                                         Ingredients              Amounts                                               ______________________________________                                         1,3-bis-[N'-(2-(5-Methyl-4-imidazolyl-                                         methylthio)ethyl)guanidino]propane                                                                      200 mg.                                               dihydrochloride.                                                               Lactose                  100 mg.                                               ______________________________________                                    

The ingredients are screened, mixed and filled into a hard gelatin capsule. 

What is claimed is:
 1. A compound of the formula: ##STR18## wherein R₁ and R₂, which may be the same or different, each represent a grouping of the structure:

    Het -- (CH.sub.2).sub.m Z -- (CH.sub.2).sub.n --

wherein Het is pyridine which is optionally substituted by lower alkyl, hydroxyl, halogen or amino; Z is sulphur or a methylene group; m is 0, 1 or 2; n is 2 or 3; and the sum of m and n is 3, 4 or 2; X₁ and X₂, which may be the same or different, are each NY wherein Y is hydroxy, cyano, CONH₂ or SO₂ R₃ or one of X₁ and X₂ is sulphur, CHNO₂, NH or N-lower alkyl; R₃ is lower alkyl, phenyl, tolyl, trifluoromethyl or amino; W is NH, and when one of X₁ and X₂ is NH, the adjoining W may also be sulphur; and q is an integer from 2 to 8; or a pharmaceutically acceptable acid addition salt thereof, provided that the sum of m and n is 2 only when Y is other than hydroxy.
 2. A compound according to claim 1 wherein W is NH.
 3. A compound according to claim 2 wherein X₁ and X₂, which may be the same or different, are NY and wherein Y is as defined in claim 1 or one of X₁ and X₂ is sulphur.
 4. A compound according to claim 1 wherein R₁ and R₂ are the same.
 5. A compound according to claim 1 wherein Z is sulphur m is 1 and n is
 2. 6. A compound according to claim 1 wherein Het is pyridine or pyridine substituted by methyl, hydroxyl or halogen.
 7. A compound according to claim 1 wherein X₁ and X₂ are the same.
 8. A compound according to claim 7 wherein X₁ and X₂ are both NCN.
 9. A compound according to claim 1 wherein q is from 2 to
 4. 10. A compound according to claim 9 wherein q is
 3. 11. A pharmaceutical composition to inhibit H-2 histamine receptors, said H-2 histamine receptors being those histamine receptors which are not inhibited by mepyramine but are inhibited by burimamide, comprising, in an effective amount to inhibit said receptors, a compound of claim 1 in combination with a pharmaceutically acceptable diluent or carrier.
 12. A method of inhibiting H-2 histamine receptors, said H-2 histamine receptors being those histamine receptors which are not inhibited by mepyramine but are inhibited by burimamide, which comprises administering orally or parenterally to an animal in need thereof in an effective amount to inhibit said receptors a compound of claim
 1. 